Did the cel come with a production pencil 
sketch?  Was that advertised on the original 
sale page?

From now on, I am going to be wary of any 
Mandarake cels without their matching sketches.

But if they could pull off production-quality 
cels off of douga they already have on hand, 
then that's going to make my job of spotting 
fakes a lot tougher.

Did the cel have a sequence number?  Was it from 
a semi-popular, recently popular, or classic 
anime?

Just wondering.